Alterations in glycosaminoglycan concentration and sulfation during chondrocyte maturation

We have used antibodies to chondroitin 4- and 6-sulfate and keratan sulfate along with Alcian blue staining of sulfated proteoglycans to investigate changes in content and sulfation within the avian growth plate. In normal chicks, chondroitin 4- and 6-sulfate content were similar in the proliferating and transitional zones but in the hypertrophic zone, chondroitin 4- and 6-sulfate were slightly lower (13% and 18%, respectively) and keratan sulfate was markedly lower (58%). Compared with the proliferative zone, Alcian blue staining of sulfated glycosaminoglycans was markedly lower in both the transitional (46%) and hypertrophic (22%) zones. In tibial dyschondroplasia, where chondrocyte maturation is arrested at the transitional zone, there was no difference in the chondroitin 4- and 6-sulfate or keratan sulfate staining between the proliferative and transitional zones, which were similar to normal birds. With Alcian blue staining there was no difference in the intensity of the staining within the proliferating zone compared with normal birds but staining in the transitional chondrocytes was markedly higher (39%). These results suggest that in the early steps of chondrocyte maturation there may be a decrease in the degree of glycosaminoglycan sulfation without any alteration in glycosaminoglycan concentration, and that further maturation may be accompanied by a change in the nature of the proteoglycans which may also affect the level of sulfation.